Gabapentin and Renal Insufficiency

April 5, 2010, 11:46 pm

★★★☆☆

Gabapentin Toxicity in Patients with Chronic Kidney Disease: A Preventable Cause of Morbidity. Zand LZ et al.  Am J Med April 2010;123:367-373.

Abstract

This retrospective study reviewed patients from 1998 to 2007 in the Mayo Clinic Rochester (MN) database with measured gabapentin levels and known medical outcomes. The study design has a number of flaws, including the fact that the authors do not describe clear methods for their review — for example, the definition of “known medical outcome” is never spelled out.  Nor are there clear goals or hypotheses for the study.  However, this paper is still worth reading because it touches on some valuable clinical pearls.

Gabapentin (Neurontin) is an anticonvulsant frequently given as an analgesic and for other off-label uses.  The drug is not bound to protein, is eliminated solely by the kidney without being metabolized, and does not interact with other drugs.  Because it is exclusively eliminated by the kidney at a rate directly related to creatinine clearance, patients with chronic renal disease are at increased risk of developing toxicity.  The article makes the following important point:

• Gabapentin toxicity is often unrecognized, and can present with coma, weakness, ataxia, drowsiness, dizziness, confusion, myoclonus and tremor.

• Many patients on gabapentin do not have regular tests for renal function, or appropriate adjustment of their gabapentin dose based on estimated creatinine clearance.

• Elevated age, multiple co-morbidities, and pre-existing central nervous system impairment may contribute to development of symptomatic gabapentin toxicity.


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